Hatchery salmon threaten wild populations, scientists say

A newly published collection of more than 20 studies by leading university scientists and government fishery researchers in Alaska, British Columbia, Washington, Oregon, California, Russia and Japan provides mounting evidence that salmon raised in man-made hatcheries can harm wild salmon through competition for food and habitat.

“The genetic effects of mixing hatchery fish with wild populations have been well-documented,” says journal editor David Noakes* from Oregon State University. “But until now the ecological effects were largely hypothetical. Now we know the problems are real and warrant more attention from fisheries managers.”

The research volume, published in the May issue of Environmental Biology of Fishes, brings together 23 peer-reviewed, independent studies carried out across the entire range of Pacific salmon, including some of the first studies describing the impact of hatcheries on wild salmon populations in Japan and Russia.

The studies provide new evidence that fast-growing hatchery fish compete with wild fish for food and habitat in the ocean as well as in the rivers where they return to spawn. The research also raises questions about whether the ocean can supply enough food to support future increases in hatchery fish while still sustaining the productivity of wild salmon.

“This isn’t just an isolated issue,” says Pete Rand, a biologist at the Wild Salmon Center and a guest editor of the publication. “What we’re seeing here in example after example is growing scientific evidence that hatchery fish can actually edge out wild populations.”

Losing wild fish would mean losing the genetic diversity that has allowed salmon to survive for centuries. Unlike hatchery fish, wild salmon populations have a range of highly specialized adaptations to the natural environment. These adaptations not only help them return to their home streams to spawn, but also increase their ability to withstand environmental changes like increases in ocean temperature and extreme variations in stream flows. Hatchery fish, as the name implies, are hatched from eggs fertilized in a controlled environment and raised in captivity until they are big enough to release into the natural environment. They lack the genetic diversity of wild fish that provides insurance against fisheries collapses.